1. Field of the Invention
The present invention relates to a numerical control device, and more specifically a numerical control device for controlling high speed response control axis without shortening control period of entire numerical control device and generating wasting waiting time.
2. Description of the Related Art
A numerical control device, can perform response control to control a control axis to be controlled corresponding to input from an external input device (such as a signal generation device, a communication device). For example, in a machine for performing punch press machining, detection signal is input to a numerical control device when it is detected that a punching tool leaves from a workpiece after hole punching by a punching tool, while the numerical control device performs response control of table axes (X axis, Y axis) corresponding to the input signal and make the workpiece to a next punching point.
In the device, high speed response with shortened control period of response control for responding as quickly as possible enables effective machining. However, in a conventional numerical control device, the control period of response control is fixed for each numerical control device, and all control axes has the same period. Therefore, it is impossible to shorten only the control period of the response control for a high response control axis which requires high speed response. In addition to that, it is possible to shorten the control period of response control by shortening the control period of entire numerical control device. However, since introduction of a high speed CPU, capable of completing all control processing in short control period, and the like, is required for shortening the control period of entire numerical control device, shortening of the control period can not be easily implemented.
Concerning an outputting technique of interpolation command for a high speed control axis, Japanese Patent Laid-Open No. 01-184506 discloses a technique in which, n pieces of command at 1/n times period of normal period (entire device) are output together at the normal period (entire device), as shown in FIG. 9.
There is a problem in the conventional numerical control device, that even when a command is input from an external device in short period for a high speed response control axis, wasting waiting time is generated from the input of command to response by the control axis, since the control axis can not read the command till the next control period.
For example, in the numerical control device descried in Japanese Patent Laid-Open No. 01-184506, the control period of response control for responding to an input command form an external input device to control the axis is fixed for each control device. Therefore, even for a axis which requires high speed response to an input command from a high speed external input device, response control is performed in the normal control period.
FIG. 10 shows a timing chart illustrating cyclic operation of an external device which outputs a command for a high speed control axis at ¼ times period of the normal control period and a numerical control device and servo control, in the numerical control device descried in Japanese Patent Laid-Open No. 01-184506. As shown in FIG. 10, the numerical control device descried in Japanese Patent Laid-Open No. 01-184506, even when a command is input at short period corresponding to period of servo control, since input detection processing and movement command calculation processing are executed in the normal period, the detection and the calculation of the movement command is waited until starting of the next control period in the control period of the numerical control machine. As a result, a case may happen in which the numerical control device can not perform high speed response and generates wasting waiting time.